Usually, an aftertreatment system is employed in an engine for treating an exhaust flow of the engine. The aftertreatment system reduces and/or converts constituents such as carbon monoxide, sulfur dioxide, nitrogen oxides and so on present in the exhaust flow into other compounds, such as H2O and N2 as per emission requirements. The aftertreatment system utilizes one or more sensors located at varying locations along the aftertreatment system. For example, a nitrogen oxide, also referred to as NOx, sensor may be located upstream and/or downstream of a Selective Catalytic Reduction (SCR) module for measuring a concentration of nitrogen oxides present in the exhaust flow entering and/or exiting the SCR module, respectively.
The SCR module may contain one or more SCR catalysts. Once exiting the one or more SCR catalysts, the exhaust stream may contain localized areas of relatively higher and lower NOx concentration. The NOx sensor positioned downstream of the SCR module may sample a region of this non-uniform exhaust flow that is non-representative of the total NOx concentration of the exhaust flow exiting the SCR module. This may provide inaccurate nitrogen oxide content readings.
In known systems, a mixing element is located upstream of the SCR module to allow for mixing of a reductant or diesel exhaust fluid (DEF) with the exhaust flow. However, this arrangement does not provide mixing of the exhaust flow downstream of the SCR module to homogenize the uneven distribution of the nitrogen oxides present in the exhaust flow received by the NOx sensor positioned post the SCR module.
U.S. Pat. No. 8,141,353 discloses such an exhaust mixer for use in an engine exhaust system downstream from an additive injector. The mixer includes a first disc-shaped wall structure with a plurality of flow openings formed therein. The mixer also includes a second wall structure carrying a set of mixer vanes. The second wall structure includes a cone shape extending radially outwardly from and intersecting the first wall structure such that the first wall structure is frusto-conical in shape.